In centrifugal discharge elevator conveyors, a plurality of spaced apart bucket containers are supported by a vertically extending conveyor chain loop. The buckets are designed to be filled during upward travel, near the bottom of the loop, raised as the loop rotates, and centrifugally discharged during the transition between upward travel and downward travel near the top of the loop during rotation about a "head" traction wheel. A problem with prior art elevator conveyors has been rapid failure of the joint between the bucket and the chain, resulting in dissociation of the bucket from the conveyor chain. This failure is caused by impact forces and centrifugal forces that act on a bucket container as it travels around the head traction wheel, as well as when it travels around the lower, or "foot" traction wheel. More particularly, in prior art elevator conveyors, when a bucket hits a traction wheel, the front edge of the bucket starts vibrating and may reach resonance. The movement of the front edge of the bucket causes deflection of the side walls of the bucket which in turn causes movement of the back of the bucket relative to the chain. This action over time results in failure of the joint between the bucket and the chain.
Another problem with prior art conveyors has been excessive noise at the wheels that guide the conveyor.
It has been heretofore proposed to use pneumatic tires in a conveying apparatus to provide a cushioning action for containers joined together with a cable, the containers being in direct driving contact with a pair of tires defining a loop. See, for example, Hapman U.S. Pat. No. 2,817,430. One problem associated with this design is that a large pneumatic tire is difficult to install and remove. In a pneumatic tire, a sudden loss of air pressure could occur and cause serious consequences. Further, for impact energy to be absorbed by the air in a tire and/or deflection of sidewalls of a tire, the pressure of air inside the tire would have to be maintained within relatively narrow limits. Temperature fluctuations, which can be caused by climatic conditions, or by heating during use of the apparatus, can cause a deviation in the path of travel of the conveyor loop, over time, potentially causing excess slack or tautness, and thereby resulting in wear of the tire and the conveyor loop. Further, a pneumatic tire would likely wear rapidly if used to engage a chain conveyor loop, as opposed to engaging containers as shown in the Hapman patent.
Another centrifugal discharge elevator is disclosed in U.S. Pat. No. 4,688,669, issued to Wobick et al. on Aug. 25, 1987, the specification of which is incorporated herein by reference.